QUESTION :
Possible Duplicate:
Can one take a partial screen shot in Windows 7?
Is there a way on Windows to just take a screenshot of the window that is the currently active one? If so, how do I do that?
ANSWER :
Press Alt–Print Screen. This copies the image of the active window onto the Clipboard. Paste the image into a graphics editing program such as Paint or GIMP, and save in your preferred image format. PNG loses no data in the image, but requires more space. JPEG is more efficient, but can show compression artifacts.
alt+printscreen captures the active window
Here is how to do it for both Windows and Mac.